1. Field of the Invention
This invention relates to an actuator for operating a pneumatically actuated switching device and more particularly to an actuator having a truncated conical housing forming an internal cavity wherein a flexible diaphragm is supported by a peripheral rib while stabilized by an edge anchor for delivering pressurized air to a remote site for triggering a switching device to produce an electrical signal in a nurse call system.
2. Description of the Prior Art
A pneumatically actuated bulb device is known in the art for a patient actuated nurse call system. An example of such a device is disclosed in U.S. Pat. No. 3,823,285 and includes deformable pneumatic bulb to provide a source of pressurized air to operate an electrical switching circuit that is well suited for use in environments where it is undesirable to use a conventional electrical switch. The possibility exists of a catastrophic explosion when a conventional electrical make-break switching circuit operates in an atmosphere containing a high concentration of a potentially explosive gas. Such an atmosphere commonly occurs in hospital rooms due to a patient's use of oxygen. A patient actuated call system is not only commonly used in hospital rooms but also in other health care facilities where there is a need or desire to summon personnel for help, particularly, when a patient is in a weakened or disabled condition. Most hospitals and health care institutions have signalling systems by which in each patient area, a patient may initiate a signal that is received at a station or at an allocated substation within a larger area to summon assistance. Typically, for example, in a hospital a select group of patient areas is serviced by a given nurse station where calls for assistance by patients are taken. Most patient areas must accommodate the use of oxygen even if it is only on an emergency basis whereby electrical switches commonly used in other industries can not be utilized. The pneumatically operated switch disclosed in the aforesaid U.S. Pat. No. 3,823,285 provides an entirely satisfactory solution to the need for a pneumatically activated switching device which can operate in a very reliable fashion in hostile environments particular atmospheres containing a high concentration of oxygen that could otherwise cause combustion. However, the deformable bulb for supplying pneumatic pressure is susceptible to improvements. As disclosed, the bulb is manufactured in one piece by an injection molding technique to avoid seams and thereby prevent leakage. A need exists for a pneumatic pressurizing device less susceptible to false triggering as can occur by any source of pressure on the bulb. Also, the pressurizing device needs to be better suited for the environment of use particularly by the selection of materials to withstand the vigorous use and abuse in the patient environment and at the same time embody a construction necessary to economic and reliability factors. In a more recent development of a pressurizing device, there is disclosed in U.S. Pat. No. 5,155,309, a pneumatic bulb embodying a generally annular ring configuration with a convexly shaped actuator dome resembling a doughnut appearance to provide a distinctive identification to the bulb for distinction from other pneumatic bulbs that may be utilized for different purposes in a patient area. The construction of the pneumatic bulb included a base plate to provide a broad area of support for the bulb and support for a peripheral rim and a center post of the doughnut shaped actuator dome. The base plate included protruding truncated conical members relied upon to maintain the doughnut shaped actuator at a fixed or pre-established location on a patient's mattress so that the patient can reliably find the bulb to summon help.
Examples of other known nurse call systems can be found in U.S. Pat. Nos. 4,702,443; 4,484,367; 4,298,863; and 3,781,843. In U.S. Pat. No. 4,702,443, a cord holding device is disclosed wherein a belt fastener is used to hold a base onto a mattress so that the base can in turn receive a cord holding member. The cord holding member supports a cord to allow limited movement of the cord the end of which carries a push button electric switch. In U.S. Pat. No. 4,484,367, a side rail of a patients bed is wrapped with a flexible sheet having a pocket in one side of the sheet for receiving an electronic push button device serving as a call device for summoning a nurse. U.S. Pat. No. 4,298,863 discloses a patient call system in which a patient operated transducer is mounted on a patients face or a portion of the body. The transducer is interconnected by pneumatic tubing to an pneumatically actuated switch that is part of an electronic monitoring system. U.S. Pat. No. 3,781,843 discloses a bed guard system in which the upper rail surfaces of patient restraining rails at opposite sides of a bed are fitted with a detector. Each detector is formed with an elongated rail engaging pocket shape to fit on the rail surface and an overlying elongated internal cavity extending generally the length of the rail. The internal cavity forms a site for a fluid material which can be pressurized by an applied pressure to the top surface of the rail covering.